RFR (XS): 8129977: TestSummarizeRSetStats.java fails: Incorrect amount of per-period RSet summaries at the end

[Thomas Schatzl]

Hi all,

  can I have reviews for the following tiny change that fixes the test
TestSummarizeRSetStats on machines with a "small" amount of available
physical memory?

The problem is that when run on machines with little memory, it issues
two young-only garbage collections instead of one.

The problem is that the test does not fix the initial heap size, which
is calculated according to available memory. This causes an additional
young GC after the first one induced by the test, messing up the
expected amount of log messages.

The reported behavior can be reproduced locally by either manually
setting -Xms to a significantly lower value than -Xmx (like 12m) or
setting MaxRAM to the same size as the machine's total physical memory
(512m - which results in a too small initial heap size of 10M, causing
this exact error).

After forcing -Xms to -Xmx in the test, it is good again regardless of
other options.

Thanks to StefanJ for observing the issue with automatic heap sizing on
the same machine for JDK-8129590 and getting me on the right track.

CR:
https://bugs.openjdk.java.net/browse/JDK-8129977

Webrev:
http://cr.openjdk.java.net/~tschatzl/8129977/webrev/

Testing:
jprt

Thanks,
  Thomas